Hack saw lift



G. J. ASPEY HACK SAW LIFT Filed Aug. 22, 1932 April 39, 1935',

3 Sheets-Sheet l HW/ENTU (5,4. sPEY HACK SAW LIFT Filed Aug. 22, 1932 5 SheetsSheet 2 a O W iii} l 1/ ,2 24 17 76 25 I 14 we 41 53 Pg 2. 9

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' HACK SAW LIFT Filed Aug. 22, 1932 3 Sheets-Sheet 3 Patented Apr. 30, 1935 Tree LQBii BSZ FFEQE Claims.

This invention relates generally to power driven hack saws, and particularly to a lift therefor.

The main object of this invention is to provide a smooth acting hack saw lift.

The second object is to provide a hack saw lift which will :furnish .a uniform amount of clearance for the teeth on the back strokeand thereby reduce to a'minimum the lifting action of the saw at each back stroke and a descending movement of the saw on the cutting stroke.

The third object is to provide a hack saw lift in which the feed can :be entirely controlled by the speed of cutting.

The fourth object is to construct a hack saw whose cutting action will be satisfactory whether it be cutting through solid stock or through thin stock in sheet or tubular form, and'regardless of its cross section.

These, and otherobjects, will become more apparent from the specification following as illustrated in the accompanying drawings, in which:

Fig. 1 is a plan view of the device showing same applied to :a draw out power hack saw.

Fig. is a section along the line 2+2 in Fig. 1 showing parts in the position of beginning the outward. stroke; namely when the saw is not cutting.

Fig. 3 is a section along the line 33 in Fig. l but showing the parts in the position during a cutting stroke.

Fig. 4 is a section taken Fig. 1.

Fig. 5 is a section taken in Fig. 4.

Fig. '6 .is a section taken along the line in Fig. 5.

Fig. 7 is a fragmentary view taken along the .line 'f-l in Fig. 1 during the cutting stroke.

.Fig. .8 is a viewsimilar to Fig. 7 but showing the return or outward stroke.

.9 is a view similar to Fig. 8 but showing an inoperative' position in which the saw is cutting very little or none at all.

Fig. 1'0 is aview similar to Fig.

along the line 4-4 'in along the line 5-5 9 in which the positions of the parts :at' the start of the cutting stroke are shown in full lines,v while the positions of the parts at the completion of the cutting stroke :are shown in dotted lines.

Similar numbers of reference refer to similar parts throughout the several views.

Referring in detail to the drawings, there is illustrated a base iii oil-which are formed the upright standards ll and 52 across which is mounted a tubular bushing 53 within which journals :a camshaft M on one end of which is a drive pulley i5, and on the other end of which is a crank it; whose connecting rod ll is joined to the saw frame l8 and the crank l6 by means of th screws 69 and it. The saw frame it carries a hack saw blade 2i. ported by a square slide 22 which is mounted in the spaced saw guides 23 and 23A, which are integral with the base 2 1 whose lowermost portion 25 is rockably mounted on the'bushing l3.

On thecam shaft i i are also thejclearance t0 cams 2G and the intermediate feed cam 21.

Rising from the'standard H is a bracket 28 which supports an upright tubular housing 29 in which is mounted a vertical plunger 3!! on whose lower end is secured a perforated nut 3! which is slidable within the lower end of the housing 29. Passing through the plunger till is a rod 32 whose lower end rests upon the feed cam El. A spring 53 is placed within the upper end of the nut 3! and the inside of the upper 2-0 end of the housing 29. The function of this spring is to urge the nut 3! downwardly toward the clearance cams 26 independently of the rod 32.

Mounted on the base NJ is a stationary rocker arm post as across whose upper end is mounted the main rocker arm 35. The post 34 isprovided with a set screw 35 adapted to serve as an adjustable stop for the rocking action of the arm 85. The end 3? of the rocker arm 35 is urged 3- toward the guide 23--A by means of a tension spring 33 which is attached between the end 31 and the saw guide tit-A.

The upper end of the guide 23A is provided with a T slot-t9 in which is disposed the head 3 ts of a screw it. The screw ll passes freely through a bushing :32 in the rocker arm end 31. The bushing 22 is rotatable with relation to the end 3". and carries on its upper end a'ratchet wheel On the top side of the ratchet wheel 49 i3 is formed a hollow hub i l in whose recess 35 is placed a cone at which is urged upwardly by a spring at. Above the cone it is placed a split nut'ccnsisting of a pair of tapered jaws 68 which are prevented from rotating by means of the pins it which project into the slots of the hub '64. The upper end of the jaws i8 is provided with an thread El which matches the thread of t e screw ii. The lower end 52 of each jaw 48 the tapering face 53 of the cone 46, and the upper end 5% of each jaw it! engages the conical recess of the threaded cap 56 which screws into the upper end of the hub id.

The purpose of the mechanism within the hub :55

The frame i8 is sup- 5 M is merely to expedite the raising of the saw out of the cut, as will be more fully explained later.

On the screw ii is secured an arm ill which is provided with an upright pin 58 which passes slidably through the end 31. The purpose of the pin 58 is merely to prevent the rotation of the screw 4 i On the main rocker arm as is an upright stand ard 59 on which is mounted a bell crank lever 56 having an approximately horizontal portion 6! and an upright portion 62. To the upright portion 62 is hinged an elongated pawl 83 whose point Ed engages the teeth 65 of the ratchet wheel 43. The lever rocks on a pin 5% on which is separately pivoted an auxiliary rocker arm 6'! one end of which is connected by a link fit to the plunger 38 by means of the screws 59. The opposite end of the auxiliary arm-El is provided with a screw it which forms an adjustable stop for the pawl 83.

The rod 32 passes through an opening H in the rocker arm 35 and engages the head E2 of an adjusting screw'lS which is locked in position on the'horizontal portion d! of the bell crank lever Ell by means of a nut it. The portion bl of the bell crank lever 752) is urged downwardly by means of a spring ?5 whose lower end is anchored to the housing 29.

In order to illustrate the invention there is shown a piece of round bar stock '15 which is being held in a vise ll. The saw cut '16 is also indicated. In Fig. 9 it is assumed that the saw '59 is dull, or that the cut is'progressing slowly, either due to the character of the metal being cut, its cross section, or other factor, while in the other views it is assumed that the saw is in proper condition and that the cutting action thereof is normal.

Before entering into a description of the operation of this invention it will be understood that in the hack saws now on the market the clearance provided for the return stroke of the saw is not measured from the bottom 8!] of the cut it, but the saw is lifted to a fixed point at each return stroke, requiring, therefore, a greater ascending and descending movement of the saw at each stroke than is required by my device in which the saw blade is lifted only the required distance for its teeth to clear the bottom 8% of the out being made.

The operation of the device is as follows: Assuming that the work 15 is suitably held in the vise ill and that the proper saw blade 2i is in position and the pulley if: being rotated by a suitable source of power (not shown) it will be seen that the rotation of the shaft i l through the crank it will cause the saw frame is to reciprocate in the saw guides 23 and Z3-A. The base 2:1, which sup ports the guides 23 and 23A, is rockably mounted on the bushing it and in the absence of any other mechanism the blade 2! would remain at the bottom of the cut; however the clearance earns 25 rotate with the shaft i l and, at the completion of the cutting stroke, the high part of each cam 26 lifts the nut 3i and its attached plunger 3s a fixed distance, causing the plunger 353 to rise and its upper end 8i to engage the under side of the perforated end of the rocker arm causing it to tip (as shown in Fig. 8) and thereby exert a downward pressure on the saw guide 23-A during the return stroke, and of course holding the teeth of the blade 25 out of a cutting position.

While the saw blade 2! is again moving in a cutting direction the feed cam 2'5 raises the rod 32 which operates the bell crank lever and consequently, through the pawl 63, turns the saw teeth should clear the when the saw has descended to a new low level it is elevateda distance, which is measured from this new low levelthat is to say, at each backward stroke of the saw it is raised to a lower elevation than it was the previous backward stroke, that is, only enough to provide the desired clearance for the saw teeth, and the faster the saw cuts the faster will be the follow-up of the clearance mechanism. In other words if it is decided that the bottom 88 of the out 18 by one sixteenth of an inch during the first return stroke and is adjusted accordingly, this clearance will be maintained on all subsequent backward strokes of the saw 2|.

' For example, the first stroke performed in the cutting off of a piece of round stock will produce a cut of a depth far in excess of what would be produced'by a similar cut performed near the diameter of the stock, thenthe more the blade 2| descends at each working stroke the more the guide 23-A rises during the same time and, due to the relationship between the rocker arm 35 and the bell crank lever 60 and associated parts, the greater the upward movement of the guide 23--A the greater will be the rotation of the ratchet wheel 13 within the limit imposed by the stop 8 i. In other Words, there is established and maintained a fixed clearance for the backward movement of the saw teeth, regardless of the cutting speed of the saw. l l

If it is desired to limit still more the follow-up action this is accomplished by means of the adjusting screw it which will decrease the period of operative engagement between the pawl 63 and the ratchet wheel 53 for a given movement/of the bell crank lever Gil. After the cut is completed or if at any time it is desired to raise the blade 2| out of the cut, this is accomplished by merely lifting the frame i8 manually which will permit the screw 4! to slip between the jaws 48, the movement of the rockerarm being resisted by the screw 35. V

From the foregoing it may be seen that there is provided a hack saw lift whose cutting action can be definitely controlled, since if this cutting speed exceeds a pre-determined maximum its cutting rate will be reduced, due to the greater period of contact between the plunger 30 and the arm 35, and during the return portion of the cycle the clearance is definitely maintained, always with relation to the bottom of the out instead of the point at which the cut was started, as is cdmmonly the case. i

.It will be noted that the two sets of cams 26 and 2?, while seemingly different in purpose, are actually intimately related to each other, the clearance cams 2% providing the lifting action for the blade on the return stroke, while the feed cam El determines the height which the blade is lifted above the bottom of the cut and, due to theinterconnection of the parts 35, 60 and 61, the regulating movement is additive to the normal lifting action so that if no out is formed by the saw there will be no decrease in the clearance, since the pawl 63 will be held out of an operative position by the screw lilj Conversely, if the saw is operating without any material it it will feed downwardly through space at a rate determined by the positions of the screws it: and i2 and by the time each cutting stroke is having a crank at of the feed cam 27 and the pin 32 in combination with the movement of the pivot center 66, move the arm 31 toward the guide 23-Athat is, increasing the distance between the stop 8| and the arm 35 to what it was at the commencement of the previous out.

It will be seen that when the clearance cam 26 raises the plunger 3t during a return stroke of the saw 28 it not only raises the saw by contacting the plunger end 5i and the part 35, but also, by means of the link 53, rocks the auxiliary rocker arm ill and permits the pawl point 6% to engage the ratchet'wheel 43 for the purpose of rotating same during the next cutting stroke of the saw 2i The pawl point 58 is rendered inoperative by the clearance cam 25 during a cutting stroke whenever the saw is unable to cut as fast as the speed for which it is set, as in Fig. 9. In other Words, the arm 6? limits the clearance and the end 3! of the plunger 35 limits the rate of cutting. Naturally, these parts do not accomplish the above-mentioned results alone but only in conjunction with other related parts. To re-state the entire matter, the saw 2! always operates within two limits, namely between a'predeten mined elevation above the bottom of thesawcut as a maximum elevation and the depth resulting from a single cutting stroke measured downwardiy from said maximum elevation.

I claim: 1

1. A lift for back saws consisting of a frame, a horizontal drive shaft mounted in said frame one end and a drive pulley at the opposite end thereof, said shaftalso having a clearance cam and a feed cam mounted thereon,

a rockable guide mounted on said frame on the axis of said shaft, a housing on said frame having an upright plunger therein actuated by said clearance cam, a rod slidably mounted along the axis of said plunger and actuated by said feed cam, a rocker arm post mounted on said frame, a main rocker arm mounted on said post having one end thereof above said plunger, said rod projecting loosely through said last mentioned portion of the rocker arm, a bell crank lever mounted on said rocker arm having a horizontal portion resting upon the upper end of said rod, spring means for urging said horizontal portion of the lever downwardly, a screw connection between the opposite end of said main rocker arm and the portion of said guide below same, a ratchet nut on said screw, a ratchet wheel for rotating said nut, a pawl actuated by said bell crank lever, and an adjustable stop for said pawl actuated from said plunger whereby a sub-normal out formed by said saw will diminish the rotation of said ratchet wheel and the corresponding lowering action of said saw.

2. A hack saw lift consisting of a rocker arm post, a main rocker arm mounted on said post, a clearance cam adapted to provide a lifting action for one end of said rocker arm during a return stroke of the saw, a ratchet-operated screw feed carried by said rocker arm adapted to change the relationship between said clearance cam and rocker arm, a pawl for operating said ratchet feed, a feed cam for actuating said pawl, and means operated by said clearance cam for controlling the action of said pawl on said ratchet feed whereby a fixed clearance will be maintained between the cutting teeth and the bottom of the out on the return strokes throughout the cutting operation.

3, A hack saw lift having in combination a slide upon which a saw can be mounted, a rockable guide for said slide, a main rocker arm mounted over rockable guide, a cam adapted to provide a lifting action during the return stroke of the saw, said lifting action being exerted under one end of said main rocker arm, the opposite end of said rocker arm having a screw depending therefrom engaging one end of said rockable guide, a nut rotating said nut, a pawl engaging said ratchet, and means operable by said cam for actuating said pawl for the purpose of rotating said ratchet wheel in a direction which will permit the sawholding end of said slide to descend a distance substantially equal to the cut formed by the previous stroke of the saw. 7

4. The substance of claim 3, together with means for varying the action of said pawl upon said ratchet wheel.

5. The substance of claim 3, and a yieldable connection between said nut and screw whereby the saw end of said slide may be raised manually out of the out, together with stop means on the support of said main rocker arm for limiting the movement thereof while said screw is being drawn through said nut.

GIDEON J. ASPEY.

for said screw, a ratchet wheel for. 

